Comiso Stone as other Sicilian carbonate lithotypes is extensively used in the Val di Noto Baroque architecture as both construction and decorative material. This study provides a petrographic and physical-mechanical characterization to evaluate its durability and response to salt weathering. Petrographic observations indicate a grain-supported texture with sparry cement, contributing to a compact rock fabric. Results show high ultrasonic pulse velocity, satisfactory compressive and flexural strength, and low water absorption, indicating reduced susceptibility to water-related decay. Salt crystallization tests reveal moderate mass variation and limited structural damage, demonstrating higher resistance to decay compared to other Hyblean calcarenites reported in the literature. The comparative analysis highlights the role of textural compactness and pore network characteristics in controlling durability. These results provide a scientific basis for assessing the long-term performance of Comiso Stone, supporting informed conservation and restoration strategies for the built heritage of south-eastern Sicily.

In this work, Etna ash-derived photocatalysts were investigated for the first time for solar H₂ production. Volcanic ash, commonly treated as a special waste in eastern Sicily (Italy), was modified through chemical treatment followed by microwave-assisted crystallization, avoiding the conventional high-temperature thermal route. The obtained material was tested both as a bare photocatalyst and as a support for a Nb₂O₅/graphitic carbon nitride composite prepared by a hydrothermal method. The Etna-derived photocatalyst exhibited a solar H₂ production rate (by TEOA photoreforming) of 920 μmol/g_cat∙h. Upon incorporation of the Nb-based composite, the H₂ evolution rate increased by about 2.5 times, reaching 2370.5 μmol/gcat∙h, demonstrating a strong synergistic effect. Notably, the developed materials largely outperformed commercial TiO₂ P25 (25 μmol/g_cat∙h). The enhanced photocatalytic activity was attributed to the tailored modifications of Etna ash, which increased porosity and promoted aluminosilicate framework reorganization, favoring an optimal distribution of the photocatalytically active TiO₂ and iron oxide phases. The obtained Nb oxide/carbon nitride supported on modified Etna ash also showed a remarkable stability after six consecutive runs of solar photocatalytic H₂ production. This work demonstrates a sustainable strategy for converting volcanic waste into efficient multifunctional photocatalysts while minimizing the use of critical raw materials.

The Monastery of San Nicolò l’Arena in Catania, a UNESCO World Heritage site, embodies a complex architectural and historical stratigraphy, reflecting successive construction phases, functional changes, and the impact of catastrophic events, including the 1669 lava flow and the 1693 earthquake. As part of the CHANGES project, this study combines historical–archaeological research with non-invasive in situ scientific analyses to investigate the materials and the conservation state of the monumental complex. Stratigraphic analysis identified multiple masonry and plaster units, allowing the reconstruction of five main construction phases and related functional changes. Portable X-ray Fluorescence (pXRF), Diffuse Reflectance Infrared Fourier Transform Spectroscopy (DRIFT), and handheld optical microscopy provided rapid insights into the chemical and mineralogical composition of plasters and mortars, highlighting lime-based binders with variable aggregate, including volcanic clasts, sand, and cocciopesto. In situ diagnostic analyses allowed us to distinguish pre- and post-earthquake materials, while historical data contextualized construction phases and functional transformations. The integration of archaeological and scientific approaches proved to be complementary: historical evidence guides the selection of analytical targets, while diagnostic results enrich and validate the interpretation of the building’s evolution. This interdisciplinary methodology establishes a robust framework for the understanding and valorization of complex cultural heritage sites.